Low odor, light color, disposable article construction adhesive

ABSTRACT

We have found a novel spray-on adhesive composition made from components including a high melt index copolymer and a high melt tackifier that interact to produce a composition that can form a low odor, light color, non-tacky, hot melt adhesive material that can be used in disposable article manufacture. The adhesive is thermally stable at hot melt application conditions, is low in cost, is easily applied and produces high quality disposable articles.

RELATED APPLICATION

This application is a continuation of application Ser. No. 11/601,177,filed Nov. 17, 2006, which application is a continuation of Ser. No.10/673,385, filed Sep. 25, 2003, issued as U.S. Pat. No. 6,846,876 onJan. 25, 2005, which claims priority under 35 U.S.C. §119(e) to U.S.provisional application Ser. No. 60/487,690 filed on Jul. 16, 2003,which applications are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to an adhesive and to a composite article made byjoining components with the adhesive. In one embodiment, a disposablearticle can be made by adhesively bonding layers including a film, awoven or non-woven fabric, tissue or sheet to a sheet-like materialusing a novel hot melt adhesive that can be variously applied or can besprayed. Still further, the invention relates to the manufacture of adisposable composite article having a cover and an absorbent layer, heldwithin the cover. The cover can be formed from a porous sheet adhered toa fluid impervious backing layer and can have further fabrics, sheets orfilms added. The absorbent layer can be made of a tissue, an absorbent,or combinations of an absorbent and outer cover layers. The adhesive ofthe invention is used to bind the components in a mechanically stablearticle or to join the outer cover to the absorbent. The sprayable hotmelt adhesive composition typically contains a novel blend ofthermoplastic copolymer and a compatible tackifying resin. Disposablearticles such as an infant or adult diaper and feminine pads can be madewith this adhesive material.

BACKGROUND OF THE INVENTION

Disposable articles and their construction materials including fabrics,films, and adhesives are described in a variety of United Statespatents. In initial work, Korpman, U.S. Pat. No. 4,028,292, teaches aheat resistant adhesive material comprising a reactive phenolformaldehyde resin and a suitable antioxidant of a metaldithiocarbamate. Collins et al., U.S. Pat. No. 4,136,699, teach adisposable article using a hot melt ABA block polymer containingpressure sensitive adhesive as a positioning and construction material.Similarly, Chen et al., U.S. Pat. No. 4,460,364, teach a hot melt PSAused in the disposables. Schmidt, Jr. et al., U.S. Pat. No. 4,526,577,teach SBS block copolymers system in disposables using multilineapplication technology. Puletti et al., U.S. Pat. No. 4,627,847, alsoteach the use of hot melts in disposables. Tsukahara, U.S. Pat. No.4,745,026, teaches a delayed tack sheet using an aqueous dispersion of,e.g., a polymer, a solid plasticizer and preferably a tackifier. Quinnet al., U.S. Patent Publication No. US 2003/0139516 A1 teach certain hotmelt adhesives utilizing a very broad range of materials. Quinn et al.,U.S. Pat. No. 6,582,829 teach certain hot melt adhesives utilizing anethylene α-olefin (EAO) polymer. The application discloses a very broadrange of materials. Dubois et al, U.S. Pat. No. 6,107,430 teach a broadrange of proposed formulations and teaches a 1000 melt index ethyleneoctene polymer (one type of EAO) combined with a tackifying resin, a waxand an antioxidant material. Werenicz et al., U.S. Pat. No. 6,120,887teach hot melt adhesive compositions using, on the whole, exemplarymaterials generally containing less than 40% of a low MI (high molecularweight) polymer material. Jialanella et al., U.S. Pat. No. 6,300,398relates to an ethylene α-olefin polymer mixture with a wax and anucleating agent to improve elongation at break of the polymer material.While the disclosure mentions the use of these materials in adhesives,no specific formulatory strategies are shown in the reference. Polymercompositions in the form of mixtures of materials are shown in thepatent from Column 20, line 50 through Column 24, line 27. Dubois etal., U.S. Pat. No. 6,319,979 teach low application temperature hot meltadhesives including an ethylene α-olefin polymer material. The patenthas a very broad disclosure, but discloses exemplary materials beginningat Column 25, line 62 through Column 30, line 36. As a whole, thematerials have less than 33% of the ethylene octene polymer (having a1000 gm-10 min⁻¹ melt index). In Table III in Column 28 further showsadditional examples using certain polymeric materials with a melt index(MI) of 500 or 1000 gr-10 min⁻¹ and in amounts less than 33 wt-%. Ahmedet al., U.S. Pat. No. 6,534,572 show compositions comprising athermoplastic component and a superabsorbent polymer material. Kroll etal., U.S. Pat. No. 6,579,915 teach certain radiation crosslinked orcurable hot melt adhesives utilizing low application temperatures. Theapplication discloses a very broad range of materials, but uses a vinylmodified block polymer a KX-222CS. The vinyl substituent on the blockpolymer is used for radiation cross-linking.

The adhesive compositions of the invention are useful for a variety ofdisposable construction applications. The adhesive is low in odor. Lowodor compositions substantially improve the working environment ofworkers who maintain equipment used in spraying the adhesive onto theworkpiece. Further, the disposable articles, when removed from theirpackaging also have little or no detectable odor which can beunacceptable to many end users. The adhesive of the invention is alsolight in color, resulting in a clear, substantially transparent glueline on the disposable materials. Typical disposables are made fromwhite or transparent, woven or non-woven fabrics, polyethylene orpolyester films and colored or charred adhesives are unacceptable insuch construction applications. The adhesive of the invention ispreferably not tacky, preferably pelletizable. Pelletizable adhesivesare relatively easy to package and use at the disposable assemblylocation. The adhesive is thermally stable such that it can be placedinto applications equipment and be maintained for a substantial periodof time at hot melt temperature prior to application.

A substantial need exists in this art to obtain such a low odor, lightcolor, non-tacky, non-pressure sensitive (pelletizable), thermallystable, hot melt adhesive. Lastly, the adhesive material of thisinvention is formulated to minimize cost, and maximize adhesiveperformance without any reduction in quality in the resulting disposablearticle.

BRIEF DISCUSSION OF THE INVENTION

We have found an improved hot melt non-pressure sensitive adhesive. Thematerial can be used as a novel spray-on adhesive composition made froma high MI polymer and a high melt tackifier component that interacts toproduce a composition that can form a low odor, light color, non-tacky,hot melt adhesive material that can be used in disposable articlemanufacture. The adhesive is thermally stable at hot melt applicationconditions, is low in cost, is easily applied and produces high qualitydisposable articles.

A first embodiment of the invention is a hot melt, preferablynon-pressure sensitive, adhesive composition. A second embodiment of theinvention is a disposable article using the hot melt adhesive in aconstruction application. A third embodiment of the invention is amethod using the hot melt of the invention to assemble a disposablearticle.

The adhesive can comprise, in its entirety, one of a number of usefulpolymers, a blend of polymers, or alternatively the adhesive cancomprise a hot melt adhesive comprising at least one polymer admixedwith other thermoplastic diluents such as tackifying resins, etc. Thepolymer provides the properties such as cohesiveness and strength. Thepolymer is typically combined with a tackifier or other material tomodify the adhesive properties for use in the intended application. Theblend of materials is formulated to exhibit the same desired properties.In this material relatively high melt or high viscosity tackifier iscombined with relatively low molecular weight (high MI) thermoplasticcomponents to enhance the cohesive strength of the mixture whilemaintaining good processability.

In production of disposables, a hot melt adhesive (HMA) is typicallyextruded at elevated temperature onto the disposable. Layers of a fabricor film can be added and blended. Disposables with secure bonding thattraps layers of fabric or tissue in the HMA can be made because theadhesive can be extruded directly on the work piece. In recent years,increasing attention has been directed to development of sprayable hotmelt adhesives. The work piece or substrate-manufacturing regimen canuse a spray-on adhesive to increase productivity. Such spray-onadhesives are delivered from a plurality of narrow orifices in the formof fibers, threads or filaments having a substantially circularcross-section with a diameter less than 0.05 inch, typically about 0.01to 0.001 inch. Fine line or spiral spray patterns are used. The spray-onadhesive takes on the form of fibers that have substantial surface areain comparison to the mass of the fiber. Typically, after spraying, theadhesives reach ambient temperatures upon immediate contact with thework piece. Extruded hot melt adhesives retain a significant amount ofheat after application. Ambient temperature is the temperature of thesurrounding environment and temperature of the disposable. In theseconstruction applications, the disposable and the temperature of theenvironment are typically not substantially different. Sprayed adhesivestake the form of a solid matrix formed as a result of the combinedapplication adhesive fibers creating an overlapping distribution ofthreads or fibers on the disposable. Spray adhesive technology is usedto make disposable articles by combining, e.g. a film with a woven ornon-woven fabric with the adhesive and forming a bond between thesubstrates or layers by pressure. Such conventional spray-on adhesivesform typically a laminated adhesive bonding with the film sheet and thefabric layers.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, a wide variety of thermoplastic polymers are suitable foruse in the invention. Such thermoplastic polymers are preferably waterinsensitive. The term “polymer” is used herein to indicate a copolymer,terpolymer, or higher order polymer, a vinyl polymer, an ethylene-basedpolymer, a block polymer or other polymer with a molecular weight andmelt characteristics that can provide useful adhesive properties. Atleast one other comonomer can be polymerized with ethylene to make thepolymer. Polymers of ethylene are those polymers having at least onecomonomer selected from the group consisting of vinyl esters of asaturated carboxylic acid wherein the acid moiety has up to 4 carbonatoms, unsaturated mono- or dicarboxylic acids of 3 to 5 carbon atoms, asalt of the unsaturated acid, esters of the unsaturated acid derivedfrom an alcohol having 1 to 8 carbon atoms, octene, hexene, and mixturesthereof. Polymers of ethylene such as ethylene-vinyl-acetate (EVA),ethylene-methyl acrylate (EMA) and ethylene n-butyl acrylate (EnBa);ethylene carbon dioxide, and mixtures thereof can be used.

Suitable ethylene/unsaturated carboxylic acid, salt and ester polymersinclude ethylene/vinyl acetate (EVA) ethylene/acrylic acid (EEA) and itsionomers; ethylene/methacrylic acid and its ionomers; ethylene/methylacrylate (EMA); ethylene/ethyl acrylate; ethylene/n-butyl acrylate(EnBA); as well as various derivatives thereof that incorporate two ormore comonomers.

A thermoplastic hot melt adhesive composition comprising a thermoplasticethylene based polymer containing at least one comonomer. Examplesinclude ethylene acrylic materials, ethylene vinyl acetate (EVA)materials and others. Such adhesives can be prepared in combination withan appropriate high petroleum based tackifying material having a definedthermal aspect. The thermoplastic, typically non-tacky adhesivecomposition comprises a thermoplastic polymer. The polymer has a meltindex grater than about 1000 grams-10 min⁻¹, often greater than 2000grams-10min. The polymer preferably has a comonomer content, e.g., avinyl acetate content of between 18 wt % to 30 wt % vinyl acetate in thecopolymer. The balance of the copolymer typically comprises the ethylenemonomer. An example of useful material typically is centered on anethylene vinyl acetate polymer containing about 20±5 wt % vinyl acetatecopolymer or an ethylene vinyl acetate material comprising about 27±5 wt% vinyl acetate comonomer. Other comonomers in the ethylene polymerspreferably comprise methacrylate, vinyl acetate, N-butyl acrylate, othersimilar unsaturated monomers and mixtures of monomers thereof can beused. The polymer material used in the invention can be derived from asingle polymeric raw material or source material or can be a blend oftwo or more polymer materials or source materials obtained from rawmaterial manufacturers. The weight ratio of a second polymeric materialto the first polymeric material used in the preparation of the adhesivesof the invention can range from about 0.01 to about 10 parts by weightof the second polymeric material per each part by weight of the firstpolymeric material. Such blends can comprise a blend of an EVA with anethylene methacrylate copolymer or a blend of an ethylene methacrylatecopolymer with an ethylene n-butylacrylate copolymer or any variationthereof.

The adhesive composition of the invention can comprises at least onehomogeneous ethylene α-olefin polymer which contains ethylene and atleast one C₃ to C₁₆ α-olefin. Such ethylene α-olefin polymers areselected based on homogeneity, density and molecular weight distribution(M_(w)/M_(n)). Useful ethylene α-olefin polymers are characterized ashaving a narrow molecular weight distribution, less than 4, preferablyless than 3, more preferably from 1 to 3, even more preferably from 1.25to 2.5. The polymers are typically homogenous and random copolymers. Anymonomer is randomly distributed within a given molecule andsubstantially all of the polymer molecules have the sameethylene/comonomer content. The homogeneous ethylene/α-olefin polymercomprises ethylene and at least one α-olefin monomer selected from thegroup consisting of an α-olefin, non-conjugated diene, and a cycloalkenesuch as propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene,1-heptene, and 1-octene, cyclopentene, cyclohexene and cyclooctene,1,4-hexadiene; 1,5-heptadiene; 4-vinyl cyclohexene;1-allyl-4-isopropylidene cyclohexane; 3-allyl cyclopentene; 4-allylcyclohexene; and 1-isopropenyl-4-butenylcyclohexene; dicyclopentadiene;alkenyl, alkylidene, cycloalkenyl, and cycloalkylidene norbornenes, suchas 5-methylene-2-norbornene; 5-methylene-6-methyl-2-norbornene;5-methylene-6,6-dimethyl-2-norbornene; 5-propenyl-2-norbornene;5-(3-cyclopentenyl)-2-norbornene; 5-ethylidene-2-norbornene;5-cyclohexylidene-2-norbornene; piperylene.

The molecular weight of the useful olefin polymer will be selected onthe basis of the desired performance attributes of the adhesiveformulation and can have a number average molecular weight of at least800 grams/mole, preferably at least 1,300 and no more than 100,000grams/mole. Ultra low molecular weight homogeneous ethylene α-olefinpolymer are considered to have a number average molecular weight of lessthan about 1,000 g/mole. For adhesive applications, the homogeneousethylene/α-olefin polymer typically has a melt index greater than about800 g/10 min., more typically greater than about 900 g/10 min.,preferably greater than about 950 g/10 min. The melt index inverselyrelates to the molten viscosity. The density of the ethylene α-olefinpolymer will be selected on the basis of the desired performanceattributes of the adhesive formulation. Typically however, thehomogeneous ethylene/α-olefin polymer will have a density of at least0.850 g/cm³, preferably at least 0.860 to 0.900 g/cm³, and morepreferably about 0.860 0.890 g/cm³.

The homogeneous ethylene α-olefin polymer will typically be present inthe adhesive of the invention in an amount greater than about 40 wt-%,preferably greater than about 50 wt-%, and more preferably greater thanabout 60 wt-%. When employing two or more homogeneous ethylene α-olefinpolymer, the first and second polymer will differ from each other withrespect to the type of monomer or the molecular weight or melt index, orthe density, or the molecular weight distribution. Accordingly, thefirst and second polymer may differ in number average molecular weightby at least 5000, preferably at least 10,000, and more preferably atleast 20,000. In addition or in the alternative, the first and secondpolymers may differ in density by at least 0.005 g/cm³, preferably by atleast 0.01 g/cm³.

The adhesive can use about 0.1 to 10 wt. % of a block polymer toincrease cohesive strength in the adhesive and increase peal strengthafter application. Block polymers useful include ABA structures, ABstructures, (A-B)_(n) radial polymers, as well as branched and graftedmaterials. The B block is typically isoprene, butadiene, hydrogenatedbutadiene, hydrogenated isoprene, etc. Commercial embodiments includethe Kraton® block polymer materials, (Shell Chemical Company, Houston,Tex.), Septon® (SEEPS) materials for Kuraray Co., Ltd., Europrene® blockpolymer materials, Sol T polymer materials (EniChem, Houston, Tex.),Vector® block polymer materials (Exxon/Dexco, Houston, Tex.). The Ablock (styrene or vinyl) content of the polymer ranges from 0.1 wt-% toabout 50 wt-%. Typically, the aromatic A block concentration ranges fromabout 5 wt-% to about 45 wt-% based on the polymer. The styrene contentcan be less than about 25 wt-%, more preferably less than about 20 wt-%and most preferably from about 5 wt-% to about 15 wt-% styrene withrespect to the total weight of the block copolymer for certainformulations. When employed with a ethylene/α-olefin polymer having arelatively high melt index, preferably the block copolymer comprises ahydrogenated block copolymer. For this embodiment the block copolymercontributes significantly to the cohesive strength of the adhesivecomposition. The molecular weight of a block copolymer relates to itssolution viscosity at 25° C., for a given weight of polymer in (toluene)solvent. The amount of block copolymer employed for determining thesolution viscosity depends on the molecular weight. For the highermolecular weight block copolymers, the solution viscosity is typicallyexpressed as a function of a 10 wt-% or 15 wt-% block copolymersolution, whereas for more conventional and lower molecular weight blockcopolymers, a 25 wt-% block copolymer solution is employed. For 10 wt-%or 15 wt-%, the solution viscosity of the block copolymer for use in theinvention ranges from about 100 cP to about 3•10³ cP at about 25° C. Fora 25 wt-% block copolymer solution, the solution viscosity may rangefrom about 10² to about 10⁵ cP, preferably from about 100 to about 8•10⁴cP, more preferably from about 200 to about 3•10⁴ and most preferablyfrom about 200 to about 2•10⁵ cP. For low viscosity adhesivecompositions, preferably the solution viscosity of the block copolymeremployed is less than 10•10³ cP, more preferably less than about 5•10³,even more preferably less than about 2.5•10³ cP and most preferably lessthan about 2•10³ cP. The block polymer is substantially hydrogenated inwhich the midblock is typically ethylene/butylene, ethylene/propylene,or mixtures thereof. Preferred block copolymers comprise substantiallysaturated materials having styrene endblocks and ethylene/butylene orethylene/propylene midblocks and having a di-block content of less thanabout 70%, a di-block content of preferably less than about 50% and morepreferably less than about 30%. The block copolymers useful hereinpreferably have a melt index of greater than about 20 grams/10 minutes,more preferably greater than about 30 g/10 min, even more preferablygreater than about 50 g/10 min. and most preferably greater than about60 g/10 min. The styrene content is preferably from about 10% to about40% by weight of the block copolymer, more preferably from about 10% toabout 35% by weight and most preferably from about 10% to about 30% byweight of the block copolymer. Other preferredStyrene-ethylene/propylene-styrene (hereinafter SEEPS) block copolymersare available from Kuraray Company, Ltd in Tokyo, Japan under thetradename of Septon®. and may also be utilized providing the blockcopolymer meets the diblock requirement. These block copolymers areuseful from about 5 wt-% to about 30 wt-% of the adhesive. Kraton®G-1650, a linear styrene-ethylene/butylene-styrene block copolymerhaving a diblock content of 0%, an M.sub.N of about 113,000 and astyrene content of about 28%; and Septon® 4033 supplied by Kuraray,Japan, a linear styrene-ethylene/propylene-styrene block copolymerhaving a diblock content of 0%, an M_(n) of about 108,000 and a styrenecontent of about 30% by weight of the copolymer. The midblocks arepreferably ethylene/butylene, ethylene/propylene or isoprene and aremore preferably ethylene/butylene or ethylene/propylene. The styrenecontent is preferably between about 10% and about 40% by weight of theblock copolymer, more preferably from about 10% to about 35% by weight,even more preferably from about 10% to about 30% by weight and mostpreferably from about 10% to about 25% by weight. The melt index ofthese block copolymers is preferably greater than about 5 g/10 min. andmore preferably greater than about 10 g/10 min. Useful examples includeKraton® 1652 available from Shell Chemical Co., a 100% linear SEBS blockcopolymer having about 29% styrene and a melt index of about 10 g/10min. These block copolymers are useful from about 5 wt-% to about 50wt-% of the adhesive, preferably from about 10 wt-% to about 50 wt-% ofthe adhesive and more preferably from about 10 wt-% to about 40 wt-% ofthe adhesive.

The composition of the present invention is preferably made by firstpreparing the thermoplastic component by melting and blending all thethermoplastic ingredients. The thermoplastic composition may bepelletized, pillowed, or cast into molds or drums, etc., for subsequentremelting and application. Alternatively, all the ingredients may be fedsimultaneously at the appropriate rates into an extruder. The preferredtackifying resins for use in the adhesives of this invention have asoftening point that is greater than about 120° C., preferably greaterthan 125° C., wherein the typical and most useful materials have asoftening point that ranges from about 127° to about 145° C. A preferredclass of tackifying resins include the petroleum hydrocarbon resins thatare very light in color, aromatic modified, cycloaliphatic hydrocarbonresins. These materials are often hydrogenated to improve thermalstability and are typically made by first polymerizing aliphaticmaterials into an amorphous polymer composition which can then be postmodified with aromatic components, hydrogenation, etc. to form a highmelting tackifying material that is particularly effective in theadhesive materials of the invention. The polymer or polymer blends ofthe invention are combined with tackifying agent in an amount thatranges from about 30 to 80 wt % of the tackifying resin, often 45 to 75wt % of the tackifying resin and in many embodiments of the inventionabout 50 to 65 wt % of the tackifying resin. In such compositions, theEVA polymer is typically present in an amount of greater than about 40wt % of the polymer or polymer blend. Typically, in the adhesives ofthis invention, the weight ratio of the polymer or polymer blend to thetackifying resin is greater than about 1:1 and the adhesive softeningpoint is typically in a range of about 70 to 82° C. (about 160 to about180° F.) or about 74 to 77° C. (about 165 to 170° F.). The polymer orpolymer blend is often used in embodiments of the invention in an amountof about 42 to 70 wt % and in a typical diaper or feminine disposable,it is used often in amounts that range from about 45 to about 65 wt % ofthe adhesive material.

The composition of the present invention may be applied by any hot meltapplication technique such as slot coating, spiral spraying, screenprinting, foaming, engraved roller or melt blown adhesive applicationtechniques. When applied in this manner, the inventive thermoplasticcomposition may be present as a coating, fiber, non-woven web, or filmlayer on at least one substrate or as a portion of an article. In oneembodiment of the disposable article of the invention, typically at aminimum, comprises at least one film combined with a non-woven or wovenfabric having a bonding layer of the adhesive of the material. Thebonding layer can typically comprise a uniform layer, a spiral spray ora sprayed on or a fine line application of adhesive composition. Theamount of adhesive combined with the film and the fabric comprises about1 to 3 milligrams/lineal inch for Fineline® applications and 1 to 8milligrams/square inch for spiral spray applications. The adhesivetypically is combined with the film or fabric by delivering thematerials at an adhesive melt application temperature to effectivelybond the film to fabric.

Ethylene Vinyl Acetate Copolymer

The preferred EVA is a high flow, 18-25 wt % vinyl acetate copolymer.TYPICAL PROPERTIES Typical Units (SI) Value¹ Resin Properties VinylAcetate wt % 18-25 Melt Viscosity 190° C. cP (mPa · sec) 3200 (3200) WaxBlend 121° C. cP (mPa · sec) 150 (150) Viscosity² Density g/cm³ 0.947Bulk Density lb/ft³ (kg/m³) 33 (530) ASTM D-1895 (B) Peak Melting ° F.(° C.) 162 (72) Temperature Physical Properties Softening Point, (° C.)80-85 R & B Tensile Strength⁴ @ Break psi (MPa) 330 (2.3) ASTM D-638Elongation⁴ @ Break % 95 ASTM D-638 Hardness, 15 s Shore A — 79 ASTMD-62240¹Values are typical and should not be interpreted as specifications.²30% MV 02520, 70% 158° F. (70° C.) melting point paraffin wax.³Physical properties were determined on compression molded specimens.⁴Tensile testing was performed on Type IV specimens.

Ethylene Vinyl Acetate Copolymer

Another preferred EVA is a 27.5 wt % vinyl acetate copolymer. TYPICALPROPERTIES Typical Units (SI) Value¹ Resin Properties Vinyl Acetate wt %25-32 Melt Viscosity 190° C. cP (mPa · sec) 3100 (3100) Wax Blend 121°C. cP (mPa · sec) 150 (150) Viscosity² Density g/cm³ 0.937 Bulk Densitylb/ft³ (kg/m³) 28 (449) ASTM D-1895 (B) Peak Melting ° F. (° C.) 144(62) Temperature Refractive Index — 1.483 Physical Properties SofteningPoint, ° F. (° C.) 169 (76) R & B Flexural Modulus, 1% psi (MPa) 640(4.4) secant ASTM D-790 Tensile Strength⁴ @ Break psi (kPa) 142 (980)ASTM D-638 Elongation⁴ @ Break % 100 ASTM D-638 Hardness, 15 s Shore A — 48 ASTM D-2240¹Values are typical and should not be interpreted as specifications.²30% MV 02528, 70% 158° F. (70° C.) melting point paraffin wax.³Physical properties were determined on compression molded specimens.⁴Tensile testing was performed on Type IV specimens.

Preferred Escorez™ 5600 Series Petroleum Hydrocarbon Resins

ESCOREZ™ 5600 Series Resins are very light color aromatic modified,cycloaliphatic hydrocarbon resins. PRODUCT SPECIFICATIONS² Grades 56005615 5637 5690 Softening Point, 100 to 106 115 to 121 127 to 133 87 to93 R & B, ° C. Color YI, Initial Color¹  6 max.  7 max.  7 max.  7 max.YI, Aged 5 hours at 75 max. 75 max. 61 max. 77 max. 175° C.¹Aromaticity, %  8 to 11  8 to 11 — 9.5 to 12  Appearance Clear, Free ofForeign Matter Melt Viscosity 140 160 180 130 (Brookfield ®) TestTemperature, 4300 3000 1800 3000 ° C. cP Molecular Weight Mw 520 560 500480 Mn 270 310 300 250 Mz 950 1000 910 900 Tg, ° C. 48 65 80 45 SpecificGravity, 1.1 1.1 1.1 1.1 10/20° C. (IPOH) Ash Content, wt % <0.1 <0.1<0.1 <0.1 Acid Number, <1 <1 <1 <1 mg KOH/g¹Solution color as determined by measurement of a 50% (by weight)product in Toluene mixture.²Exxon Mobil ® Test Methods, some of which were developed from ASTM testmethods, are available upon request.

EASTOTAC® Resin H-142R Product Data Sheet

Typical Value, Property Test Method Units Ring and Ball Softening Point142° C. Color, Gardner Molten 4 in 50% Toluene D6166 1.5 YellownessIndex in 50% Toluene E313 11 Density 1.04 g/mL Viscosity, Brookfield ® @190° C. 3000 cP Form Flake Acid Number <0.1 Bulk Density 1.04 g/mLBromine Number 5 Flash Point Cleveland Open 321° C. (610° F.) Cup

DETAILED DISCUSSION OF THE INVENTION

The articles of the invention at a minimum comprise a film layer or apermeable layer adhesively joined with a substrate. The permeable layercan comprise a cellulosic tissue, a woven or non-woven fabric or otherthin, flexible, porous or wettable sheet-like material. The tissue layeris a well known, typically loosely formed cellulosic sheet of highporosity or permeability. The fabric layer consists of a fluid permeableflexible material that can be made of either hydrophilic or hydrophobicfiber components. Woven and non-woven webs comprising the fabric cancomprise natural or synthetic fibers or mixtures thereof. Woven andnon-woven materials are well known and their construction methods havebeen practiced for many years. Woven fabrics are typically manufacturedin weaving machines forming an interlocking mesh of fibers forming thelayer. Non-woven fabrics can be made through a dry-laid or wet-laidmethod in carding processes, air laying processes or spun bond processesto produce a web that is mechanically, chemically or thermally formed.The fabric layers for use in the compounds and articles of thisinvention typically have a basis weight in the range of about 10 to 25,preferably 14 to 18 grams per square yard, a minimum dry tensilestrength of at least 800 grams per cm² in the machine direction, and atleast 200 grams per cm² in a cross machine direction. Syntheticmaterials commonly used in forming the fabric top sheets include rayon,polyester, polypropylene, polyethylene, nylon and others.

The substrate materials that can be used in the manufacture of thedisposable articles of the invention, in combination with the tissue orwoven or non-woven fabric, comprises any typical substrate used in themanufacture of disposable articles including films, sheets, elastics,absorbents, cellulosic fluffs or fill, other tissue, woven or non-wovenfabrics, etc.

Absorbent layers can be adhered to other substrates using the adhesivesof the invention. Such absorbent layers can comprise cellulosic pulp orfluff. Such fluff layers are often formed and wrapped in tissue toprovide mechanical integrity to the fluff which has little inherentintegrity. Fluff is typically manufactured through formation ofcellulosic fibers. However, other materials can be utilized to form highabsorbent fluff or pulp layers.

Elastic bands or elements can be used in the manufacture of thedisposable articles of this invention.

The film or sheet-like layer used in the invention comprises a flexiblesheet-like or film substrate. Such films are typically manufactured fromthermoplastic resins and take the form of a thin layer having athickness of about 0.5 to 2.0 mils. Such films comprise polyethylene,polypropylene, ethylene-propylene copolymers, ethylene acrylatecopolymers, ethylene vinyl acetate copolymers, polyvinyl chloridepolymers, polyvinylidene chloride polymers, polyester polymers andothers. Such films can be perforate or imperforate. In addition to theabove materials used in the composite articles of the invention, avariety of other materials can be used, including other wrappingmaterials, deodorants, perfumes, dyes, and decorative appliqués, whichprovide further absorbency, instructional legends, and pleasingappearance or smells.

In somewhat greater detail, the adhesives of the invention can be usedin the manufacture of disposable articles including disposable diapers,incontinent devices or diapers, feminine pads, and disposable bed padsby adhering a porous layer to a substrate. The assembly operations thatdeserve note include adhering a porous non-woven layer to a back sheetand adhering a tissue layer to an absorbent core.

In the manufacture of absorbents for disposables, it is common to wraploosely assembled fluff or batts of absorbent material within a tissueoverwrap. In such manufacture, the tissue surrounds the absorbentmaterial in an overlapping fashion such that the spray-on adhesive canbe applied to the overlap area, causing the adhesive to penetrate theoverlap to contact the underlying fluff or batt. The spray-on adhesivein contact with the tissue and absorbent material forms a strongmechanical bond which maintains the tissue wrap and provides mechanicalsupport and integrity to the underlying fluff or absorbent battmaterial. As a result of using the manufacturing techniques of theinvention, the tissue-covered absorbent material obtains substantialmechanical integrity from the adhesive and tissue structure. During use,the tissue and adhesive maintains the fluff or batt in place andprevents movement of the absorbent material resulting in aninappropriate segregation of absorbent material in a small portion ofthe absorbent article. Such mechanical integrity insures that theabsorbent material stays in place to provide absorbency and protection.

In the manufacture of composite articles, the fluid permeable fabric topsheet is adhered to a film back sheet. An absorbent layer can beintroduced into the space between the fabric layer and the back sheet.Typically a fluid in contact with the fabric layer passes through thefabric layer and is absorbed and held within the absorbent layer. Theabsorbent core typically comprises a highly porous, highly absorbentloosely contacted fluff, wrapped or encased within a tissue cover. Theabsorbent fluff typically has little mechanical integrity. The tissuewrap or cover, once adhered to the fluff, provides the absorbent layerwith substantial dimensional integrity preventing the absorbent materialfrom migrating or collecting in an inappropriate portion of the diaper.The tissue wrap ensures that the absorbent material remains evenlydistributed within the envelope created by the back sheet and the fabriclayer. The manufactured diaper or the components of the diaper can haveelastic bands or segments adhesively attached to provide security forthe wearer. such elastic bands create a snug fit at the waist and theleg apertures of the disposable articles. The adhesive compositions ofthe invention can be used to form bonds between the surfaces of the filmmaterials between apertured films and non-apertured films, betweentissue and non-woven or woven fabric layers, between absorbent fluff andtissue overwraps, and between elastic bands or elements and anystructural component of the disposable diaper.

In construction methods for the preparation of the disposable articlesof the invention, the adhesives are typically applied from spray headsthat deliver the adhesive at elevated temperatures (typically aboveabout 250° F. and typically in the range of 275°-400° F.). The sprayheads have apertures that range from about 0.01 to about 0.04 inch.Under the operating conditions of typical adhesive spray machines, thediameter of the sprayed adhesive fiber can range from the size of theaperture to as little as about 0.001 inches depending on operatingconditions. Depending on the end use and final bond strength desired,the adhesive can be used at application amounts that range from 0.5milligrams per square inch to as much as 10 milligrams per square inch.preferably, because of the unique properties of the adhesives of thisinvention, the adhesives can be used at an application amount of fromabout 0.5 milligrams per square inch to 5 milligrams per square inch.Most preferably, in disposable diaper construction the adhesive of theinvention is used at an application rate of about 1 to about 4milligrams per square inch.

During the manufacture of disposable articles using the adhesives of theinvention, two modes of application are preferred. One mode of operationinvolves spraying the adhesive upon a fabric, such as a tissue, a wovenor non-woven web, or other material having permeability to the adhesive.Such sprayed-on adhesive can penetrate the permeable tissue, non-wovenor woven fiber, to cause the sheet to be embedded in the adhesive andadhered to the substrate such as an absorbent layer, back layer, orfilm. Alternatively, the adhesives of the invention can be directlyapplied to back sheet or film and the tissue, woven or non-woven fabric,or other material can be applied to the adhesive on the film. Theadhesive retains sufficient liquidity that it can penetrate pores orapertures in the fabric to form a mechanical bond. In the manufacture oftissue fluff absorbent cores, the fluff is typically wrapped by tissue.the tissue layer can be wrapped around the fluff and can overlap.Adhesive can then be sprayed on the overlapping portion of tissueouterwrap, can penetrate the wrappings and adhere the tissue to thefluff ensuring that the fluff obtains dimensional stability fromadherence to the outer wrap.

In somewhat greater detail, the sprayable, hot melt adhesivecompositions of the invention typically comprise an effective amount ofa base and an effective amount of a tackifying agent to form aneffective adhesive that has the unique property that after spraying andcooling retains sufficient liquidity to penetrate a porous layer. TABLE1 EVA Based Adhesive EVA >40 42-80 45-75 Second EVA  0-40 10-30 15-25Tackifier 30-80 45-75 50-65 Wax 0-5 0-5 0-5 STAB   0-0.2 0.01-0.2 0.01-0.2 

TABLE 2 EAO Based Adhesive EAO 35-85 30-80 50-75 Second Polymer  0-4010-30 15-25 Tackifier 30-80 45-75 50-65 Wax 0-5 0-5 0-5 STAB   0-0.20.01-0.2  0.01-0.2 

TABLE 3 EAO/ABA Based Adhesive EPO 35-85 40-80 45-75 ABA 0.1-10  0.2-8 0.3-6  Tackifier 30-80 45-75 50-65 Wax 0-5 0-5 0-5 STAB   0-0.20.01-0.2  0.01-0.2 

The hot melt adhesives of the invention are made in common hot meltmanufacturing equipment. In the manufacture of the hot melt adhesives ofthe invention, the EVA copolymers typically added to a melt comprisingeither the tackifier or the plasticizer material or mixtures thereof.Such additions facilitate the blending of the EVA copolymer into asmooth, uniform mixture. In such a manufacturing regimen, either thetackifier or the plasticizer or a portion thereof is added to themanufacturing equipment under inert atmosphere and is heated andagitated until melted. The EVA copolymer is then added to the melt at arate such that the mixture forms a uniform smooth blend within areasonable period. Antioxidant materials used in the manufacture of theadhesive can be added to the melt prior to, with, or after the additionof the block copolymer. Once a smooth blend of the copolymer inconjunction with an adhesive component is formed, the balance of thecomponents of the hot melt adhesives can be added at a convenient rate.Once the uniform blend of all the adhesive ingredients is formed, theadhesive can be drawn off and packaged in a convenient form including indrums, blocks, pillows, pellets, granules, etc.

The following examples provide additional information with respect tothe manufacture of the adhesives of the invention and include the bestmode. Following the standard laboratory blending procedures thefollowing compositions were blended into a hot melt adhesive:

EXAMPLES 1-13

The table below is a summary of data generated for these products. About2000 g batches of each were made by melt blending in a lightning mixerat 300° F. The Brookfield® Thermosel viscosity and Mettler® SofteningPoint were measured. We laminated polyethylene and non-woven films usinga Nordson® spiral spray head. We used both spiral spray and Fineline®patterns. The non-woven/polyethylene laminate was tested for initialT-peel adhesion.

The best products have a maximum initial spiral spray value with minimalfalloff of aged spiral spray values. The best products appear to bethose with 25-30% tackifying resin and EVA primarily composed of 20%vinyl acetate. Products that are made completely from 28% vinyl acetateEVA tend to be soft and can have cohesive problems. The lower vinylacetate EVA is more crystalline and cohesive. Spiral peel Fineline ®peel Viscosity Softening Example Escorez ™ EVA EVA Initial Aged InitialAged @ 149° C. Point Nbr. 5637 28/2500 20/2500 (g) (g) (g) (g) 300° F.(° F.) 1 0.15 0.425 0.425 11 85 56 53 7250 174 2 0.2 0.6125 0.1875 70107 67 118 6465 169 3 0.25 0.75 0 102 180 44 68 6125 165 4 0.35 0 0.65107 121 21 38 4410 174 5 0.25 0.1875 0.5625 57 170 60 82 5410 171 6 0.30.5125 0.1875 125 127 37 52 5300 166 7 0.35 0.325 0.325 117 148 49 714444 169 8 0.15 0 0.85 28 117 88 60 6750 176 9 0.15 0.85 0 67 73 59 347000 167 10 0.15 0 0.85 28 54 104 63 6680 177 11 0.35 0.65 0 49 345 4546 4310 170 12 0.35 0 0.65 92 93 17 27 4680 174 13 0.31 0.35 0.34 78 18860 83 4750 170

EXAMPLES 14-19

The table below is a summary of data generated for the ethylene olefinproducts. About 2000 g batches of each were made by melt blending in alightning mixer at 300° F. The Brookfield® Thermosel viscosity andMettler® Softening Point were measured. We laminated polyethylene andnon-woven films using a Nordson® spiral spray head. We used both spiralspray and Fineline® patterns. The non-woven/polyethylene laminate wastested for initial T-peel adhesion 120° F. Example Example ExampleExample Example Example 14 15 16 17 18 19 Ethylene/octene 70.0 65.0 65.060.0 polymer EVA 28% 69.8 EVA-2500 MI ABA¹ 5.0 ABA² 5.0 EVA 20% 69.8EVA-2500 MI Eastotac ® 142 30.0 30.0 tackifier Escorez ® 5637 29.8 34.829.8 34.8 tackifier Irganox ® 1010 0.2 0.2 0.2 0.2 0.2 0.2 antioxidantSpiral Peel 93 38 111 143 (Initial) Adhesion Fineline ® Peel 89 35 72 96(Initial) Adhesion Viscosity @ 5380 5210 8480 7600 300° F. Mettler ® 170175 172 174 Softening PointThe ethylene/octene polymer is a 1000 MI ethylene octene (density ofabout 0.860 to 0.890) polymer. The peel values of the Ex. 17 areequivalent to what are obtained from the best commercially available SBC(PSA) based products on the market. Similar quality was obtained in Exs.14 and 16. Examples 17 and 18 are prepared in 2000 g batches by meltblending in a lightning mixer at 300° F. ABA¹ is a SEPS Kraton® G1652,ABA² is a SEEPS Septon® 4033.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

1. A hot melt adhesive composition comprising a) greater than about 40weight percent of an ethylene comonomer copolymer composition having amelt index of greater than about 800 gm-10 min⁻¹, the comonomercomprising vinyl acetate, methyl acrylate, ethyl acrylate, n-butylacrylate, acrylic acid, salts of acrylic acid, methacrylic acid, saltsof methacrylic acid, or mixtures thereof; b) an effective amount of anaromatic modified, cycloaliphatic hydrocarbon resin having a softeningpoint of about 100° C. or greater, wherein the weight ratio of thecopolymer composition to the resin is greater than 1:1.
 2. The hot meltadhesive composition of claim 1 wherein the aromatic modified,cycloaliphatic hydrocarbon resin is an amorphous polymer composition. 3.The hot melt adhesive composition of claim 1 wherein the adhesivecomposition comprises greater than about 30 weight percent of aromaticmodified, cycloaliphatic hydrocarbon resin.
 4. The hot melt adhesivecomposition of claim 1 wherein the softening point is about 100° C. 5.The hot melt adhesive composition of claim 1 wherein the softening pointof the tackifier is at about 120° C. or greater.
 6. The hot meltadhesive composition of claim 1 wherein the copolymer compositioncomprises poly ethylene vinyl acetate.
 7. The hot melt adhesivecomposition of claim 6 wherein the ratio of the copolymer composition tothe resin is about 60:40.
 8. The hot melt adhesive composition of claim6 wherein the ratio of the copolymer composition to the resin is about65:35.
 9. The hot melt adhesive composition of claim 1 wherein theadhesive softening point is about 70° C. to 82° C.
 10. A disposablearticle comprising a film layer bonded to a non-woven layer using a hotmelt adhesive composition, the adhesive composition comprising: a)greater than about 40 weight percent of an ethylene comonomer copolymercomposition having a melt index of greater than about 800 gm-10 min⁻¹,the comonomer comprising vinyl acetate, methyl acrylate, ethyl acrylate,n-butyl acrylate, acrylic acid, salts of acrylic acid, methacrylic acid,salts of methacrylic acid, or mixtures thereof; b) an effective amountof an aromatic modified, cycloaliphatic hydrocarbon resin having asoftening point of about 100° C. or greater, wherein the weight ratio ofthe copolymer composition to the resin is greater than 1:1.
 11. Thedisposable article of claim 10 wherein the aromatic modified,cycloaliphatic hydrocarbon resin is an amorphous polymer composition.12. The disposable article of claim 10 wherein the adhesive compositioncomprises greater than about 30 weight percent of aromatic modified,cycloaliphatic hydrocarbon resin.
 13. The disposable article of claim 10wherein the softening point of the tackifier is about 100° C.
 14. Thedisposable article of claim 10 wherein the softening point of thetackifier is about 120° C. or greater.
 15. The disposable article ofclaim 10 wherein the copolymer composition comprises poly ethylene vinylacetate.
 16. The disposable article of claim 15 wherein the ratio of thecopolymer composition to the resin is about 60:40.
 17. The disposablearticle of claim 15 wherein the ratio of the copolymer composition tothe resin is about 65:35.
 18. The disposable article of claim 10 whereinthe adhesive softening point is about 70° C. to 82° C.
 19. Thedisposable article of claim 10 wherein the adhesive composition isprovided as a uniform layer, a spiral spray layer, or a fine line layer.20. The disposable article of claim 19 wherein the adhesive is appliedat about 1 to 8 milligrams per lineal inch.
 21. The disposable articleof claim 19 wherein the adhesive is applied at about 1 to 3 milligramsper lineal inch.
 22. The disposable article of claim 10 wherein thenonwoven layer comprises rayon, polyester, polypropylene, polyethylene,nylon, or a copolymer or mixture thereof.
 23. The disposable article ofclaim 10 wherein the film layer comprises polyethylene, polypropylene,ethylene-propylene copolymers, ethylene acrylate copolymers, ethylenevinyl acetate copolymers, polyvinyl chloride polymers, polyvinylidenechloride polymers, polyester polymers, or copolymers or blends thereof.24. The disposable article of claim 10 further comprising sheets,elastics, absorbents, cellulosic fluffs or fill, tissue, or acombination thereof.
 25. The disposable article of claim 10 wherein thedisposable article comprises a disposable diaper, an incontinent device,a feminine pad, or a disposable bed pad.